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The Bouncy Castle Java APIs for the TLS, including a JSSE provider. The APIs are designed primarily to be used in conjunction with the BC FIPS provider. The APIs may also be used with other providers although if being used in a FIPS context it is the responsibility of the user to ensure that any other providers used are FIPS certified and used appropriately.

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package org.bouncycastle.tls.crypto.impl;

import java.io.IOException;

import org.bouncycastle.tls.AlertDescription;
import org.bouncycastle.tls.ProtocolVersion;
import org.bouncycastle.tls.TlsFatalAlert;
import org.bouncycastle.tls.TlsUtils;
import org.bouncycastle.tls.crypto.TlsCipher;
import org.bouncycastle.tls.crypto.TlsCryptoParameters;
import org.bouncycastle.tls.crypto.TlsDecodeResult;
import org.bouncycastle.tls.crypto.TlsEncodeResult;
import org.bouncycastle.tls.crypto.TlsHMAC;

/**
 * The NULL cipher.
 */
public class TlsNullCipher
    implements TlsCipher
{
    protected final TlsCryptoParameters cryptoParams;
    protected final TlsSuiteHMac readMac, writeMac;

    public TlsNullCipher(TlsCryptoParameters cryptoParams, TlsHMAC clientMac, TlsHMAC serverMac)
        throws IOException
    {
        if (TlsImplUtils.isTLSv13(cryptoParams))
        {
            throw new TlsFatalAlert(AlertDescription.internal_error);
        }

        this.cryptoParams = cryptoParams;

        int key_block_size = clientMac.getMacLength() + serverMac.getMacLength();
        byte[] key_block = TlsImplUtils.calculateKeyBlock(cryptoParams, key_block_size);

        int offset = 0;

        clientMac.setKey(key_block, offset, clientMac.getMacLength());
        offset += clientMac.getMacLength();
        serverMac.setKey(key_block, offset, serverMac.getMacLength());
        offset += serverMac.getMacLength();

        if (offset != key_block_size)
        {
            throw new TlsFatalAlert(AlertDescription.internal_error);
        }

        if (cryptoParams.isServer())
        {
            writeMac = new TlsSuiteHMac(cryptoParams, serverMac);
            readMac = new TlsSuiteHMac(cryptoParams, clientMac);
        }
        else
        {
            writeMac = new TlsSuiteHMac(cryptoParams, clientMac);
            readMac = new TlsSuiteHMac(cryptoParams, serverMac);
        }
    }

    public int getCiphertextDecodeLimit(int plaintextLimit)
    {
        return plaintextLimit + writeMac.getSize();
    }

    public int getCiphertextEncodeLimit(int plaintextLength, int plaintextLimit)
    {
        return plaintextLength + writeMac.getSize();
    }

    public int getPlaintextLimit(int ciphertextLimit)
    {
        return ciphertextLimit - writeMac.getSize();
    }

    public TlsEncodeResult encodePlaintext(long seqNo, short contentType, ProtocolVersion recordVersion, int headerAllocation,
        byte[] plaintext, int offset, int len) throws IOException
    {
        byte[] mac = writeMac.calculateMac(seqNo, contentType, plaintext, offset, len);
        byte[] ciphertext = new byte[headerAllocation + len + mac.length];
        System.arraycopy(plaintext, offset, ciphertext, headerAllocation, len);
        System.arraycopy(mac, 0, ciphertext, headerAllocation + len, mac.length);
        return new TlsEncodeResult(ciphertext, 0, ciphertext.length, contentType);
    }

    public TlsDecodeResult decodeCiphertext(long seqNo, short recordType, ProtocolVersion recordVersion,
        byte[] ciphertext, int offset, int len) throws IOException
    {
        int macSize = readMac.getSize();
        if (len < macSize)
        {
            throw new TlsFatalAlert(AlertDescription.decode_error);
        }

        int macInputLen = len - macSize;

        byte[] expectedMac = readMac.calculateMac(seqNo, recordType, ciphertext, offset, macInputLen);

        boolean badMac = !TlsUtils.constantTimeAreEqual(macSize, expectedMac, 0, ciphertext, offset + macInputLen);
        if (badMac)
        {
            throw new TlsFatalAlert(AlertDescription.bad_record_mac);
        }

        return new TlsDecodeResult(ciphertext, offset, macInputLen, recordType);
    }

    public void rekeyDecoder() throws IOException
    {
        throw new TlsFatalAlert(AlertDescription.internal_error);
    }

    public void rekeyEncoder() throws IOException
    {
        throw new TlsFatalAlert(AlertDescription.internal_error);
    }

    public boolean usesOpaqueRecordType()
    {
        return false;
    }
}